Adding hotkeys for authoring Touch UI. Fixes #248.

Added support for hotkeys in touch ui. 

ctrl+shift+e for edit layer
ctrl+shift+p for preview layer
ctrl+shift+a for annotate layer
ctrl+shift+d for developer layer
ctrl+shift+t for targeting layer
ctrl+shift+s to toggle sidepanel
I thought they might be constants defined in the authoring clientlib, but I see that they are not. There's no point IMHO of making them constants here.